The Jason-1 OSDR-SSHA product is aimed towards providing near-real-time (NRT) sea surface height anomaly (SSHA) measurements from the Jason-1 mission. The product is very similar to the NRT OSTM/Jason-2 GPS-OGDR-SSHA ... product. Both are provided as NetCDF files.

The primary difference between the two products is that the most accurate NRT SSHA measurements are provided in the field: ssha_dyn - on the Jason-1 OSDR-SSHA product gps_ssha - on the OSTM/Jason-2 GPS-OGDR-SSHA product.

WARNING: The field "ssha_dyn" on the Jason-1 product has been globally leveled to "gps_ssha" on the OSTM/Jason-2 product. So, for example, "ssha_dyn" and "gps_ssha" both have a bias of approximately 174 mm with respect to absolute calibration sites, such as the Harvest platform. This facilitates easier simultaneous application of the Jason-1 and Jason-2 NRT SSHA products for operational oceanography.

The OSDR-SSHA product is available with a typical latency of 7 hours from the last available measurement on each data file, and the orbit altitude used to generate ssha_dyn has accuracies of <= 2 cm (RMS).

Note that the OSDR-SSHA product also provides an alternative SSHA measurement in a field named "ssha". This field is identical to "ssha_dyn" except that it is derived using the DORIS-DIODE orbit altitudes from the Jason-1 OSDR, which have accuracies of 10-20 cm.

Sources of data on the Jason-1 OSDR-SSHA product ------------------------------------------------

The Jason-1 OSDR-SSHA product is generated from: 1) Altimeter and radiometer data provided on the Jason-1 Operational Sensor Data Record (OSDR). 2) Forecast pressure fields from the National Center for Environmental Prediction (NCEP). There are used for the dry troposphere and inverse barometer corrections. 3) Pole location predictions from the International Earth Rotation Service (IERS) Bulletin A product, for the pole tide correction. 4) Ancillary geophysical models (solid Earth and ocean tides, mean sea surface, sea state bias) that are consistent with the Jason-1 GDR-C standards. The one exception is that the S1 and M4 ocean tides are not included in the ocean tide model field, ocean_tide_sol1. 5) Orbit altitudes derived from SSHA crossover differences with measurements on the NRT OSTM/Jason-2 GPS-OGDR-SSHA product. This implicitly levels ssha_dyn, from the Jason-1 OSDR-SSHA product, and gps_ssha, from the OSTM/Jason-2 GPS-OGDR-SSHA product.